Phosphorite Flashcards
Sedimentary Phosphorite
is a marine chemical sediment commonly associated with upwelling
Increasing import source of
Uranium
Use phosphorite to get the P out to apply
as fertiliser and recycle it
Phosphorite rock started to increase when
things started living in the ocean
Phosphorite: continental margin
- Linked to ocean circulation
- P is coming up with upwelling
- Tends to form underneath upwelling zones provided there is low accumulation rate (needs time as a slow former)
To get phosphorite:
- decaying organic matter (the more the better) + low sediment accumulation rates
Economic Phosphorite
- High nutrients required (either mesotrophic or eutrophic)
Phosphogenesis
- Bacteria breaks down organic matter and releases phosphate to pore water. This concentrates P in their cells and promotes phosphogenesis
- As remains come to the bottom, they are decaying on the seafloor
- They break down and form HPO4(2-), and if trapped in the sediment pile, you get francolite
- If you have porous sediments, P will flux back into seawater and feed the next generation of organisms
- Bacteria can help trap P - eutrophic seetings can help phosphorite
Economic Phosphorite
- Forms through the upwelling, phosphogenesis and reworking of pristine phosphorite into granular deposits
- Upwelling provides p to the surface of the ocean and supports blooming phytoplankton
Upon death, phytoplankton fall to the seafloor where the are consumed by bacteria.
Bacteria releases phosphate to pore water and promote phosphogenesis - Storm currents rework and concentrate pristine phosphorite into high-grade granular beds
- Can keep it there or rework it (reworking will slowly decay of it but not fast enough to get rid of it
Pristine:
- in situ precipitation of francolite within sediemnt (authigenic) to produce a laminated or nodular phosphorite
Reworked
Winnowing, reworking, and transport of pristine phosphorite to produce granular deposits
Stratigraphic condensatio
- stabilises the zone of phosphogenesis (ZOP) within the sediment for continual, long term precipitation of francolite
- Reworks pristine phosphorite into granular phosphatic deposits
- Anywhere there is a condensed section is useful
- high sea level will starve shelf (accumulation decreases) from stratigraphic columnisation and make it ideal for phosphorite
Phosphirite giants
- form in epeiric seas (inland sea)
Controls on the formation of economic phosphorite
Sea level high stands and shelf slope.
- elevated sea leavel allows upwelling and stratigraphic condensation to occur over a larger area = wide spread phosphogenesis
- these factors are accentuated in epeiric seas = phosphorite giants
- Sequence stratigraphy can be used as a predicting tool to explore for economic phosphorite
Most limiting factors that determine the yield potential
- Light
- Heat
- Mechanical Support
- Organic Matter
- Phosphorous
- Potassium
- nitrogen
- Other nutrients
- Water
- Air
Glauconite and Phosphorite
Glauconite and phosphorite often go together as sedimentary authigenic minerals because they both need low accumulation rates
- Bacteria in phosphogenesis create a semi-reducing environment
